Man’s range of knowledge (3)
I believe the answer is:
ken
I believe this is a double definition.
'man's' is the first definition.
'range of knowledge' is the second definition.
(I've seen this before)
(Other definitions for ken that I've seen before include "Understanding - boy's name" , "One's range of knowledge" , "Notice" , "Know; man's name" , "Awareness" .)